<!DOCTYPE html>
<html lang="zh-CN">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <script>
    // let num = 10
    // console.log(typeof num);

    // let str = '泽哥'
    // console.log(typeof str);

    // let str = '10'
    // console.log(typeof str);

    // let flag = true
    // console.log(typeof (flag));

    // let flag 
    // console.log(typeof flag);

    let flag = null
    console.log(typeof flag);
  </script>
</body>

</html>